Electrical plug



March 4, 1941. G. H, BURT 2,233,909

ELECTRICAL PLUG Filed Aug. 29, 1958 NVENTOR.

A TTORNEYS.

Patented Mar. 4, 1941 UNITED STATES PATENT OFFICE 1 Claim.

This application is a continuation in part of my pending application Serial No. 197,557, iiled March 23, 1938 and issued as Patent No. 2,128,883.

This invention relates to an electrical connector or plug, and more particularly to an improved electrical cord connector plug of the type commonly employed to attach a circuit cable or extension cord to a heater such as an electric iron, toaster or other electrical appliance.

An object of the invention is to provide an improved electrical connector construction having means whereby the electrical contacts and the connector wires attached thereto within the plug are relieved from extreme pulling strains such as when the plug is Withdrawn from the socket of the appliance by seizure of the cable.

Another object of the invention is to provide an improved cord connector plug construction having means for firmly gripping and anchoring the extension cord or cable thereto whereby the plug may be easily separated from the socket by a straight axial pull on the cable Without iniiicting detrimental vstrain on either the connector $5 Wires or the contacts within the plug structure.

Another object of the invention is the provision .of an electrical cord connector of the above character having anchoring means for the extension cord as it emerges from the plug designed so as to relieve the contact and connector wires within the structure from torsional strain when the extension cord is subjected to a torque by being twisted.

Another object of the invention is to provide an electrical plug and cord assembly in which the grip on the cord will be suiiicient to prevent within certain tolerances a pull or torque applied to the cord outside of the plug from being so transmitted to the'part of the cord Within the 40 Plug as to cause'a movement of the cord parts within the plug beyond certain limits.

Another ofbject of the invention is the provision 0f a pair of members so shaped that they may be molded with all parts of each of the members integral with its member and with no undercut or overhanging portions which would prevent the same from being withdrawn from a mold.

A further object of the invention is to provide the gripping portions of the mem-bers which engage the cord in spaced relation so that two distinct points of gripping may 'be had to one assist the other in performance of the desired holding function.

With these and other objects in view. the invention consists of certain novel features of construction, as will be more fully described, and particularly pointed out in the appended claim.

In the accompanying drawing:

Fig. 1 is a vertical elevational View of an electrical cord connector plug formed of a pair of sections in opposed face to face relation embodying my invention;

Fig. 2 is an elevational view of the connector plug structure in Fig. l but with the front section removed;

Fig. 3 is a detail view, in elevation, of the front section of the connector plug structure in Fig. 1, showing the anchoring means for the extension cord; and

Fig. 4 is a sectional View substantially on line 4 4 of Fig. 3 but showing both front and rear plug sections together.

It is well-known practice in the use of ordinary electrical cord attachment plugs that such devices are many times Withdrawn from the socket of the electrical appliance by seizure and sudden jerking of the calble or extension cord, thereby causing extreme strain to be imposed on the connection wires of the cable with the contacts of the plug and consequently resulting in a. rapid destruction and deterioration of the portion of the cable adjacent to the plug. Further, twisting of the cord often occurs causing a different strain to be transmitted to and into the plug. i

The strain placed on these extension cords vunder these conditions often is of such force that many times the connector wires of the cable Where they are attached to the metal contacts of the plug are broken and short circuits result; and in order to o-bviate such difficulties I have provided an electrical cord connector plug construction having means disposed within the plug so constructed and arranged as to prevent the connection `between the wires and the contacts Within the plug from being materially strained by reason of excessive tension or torque being transmitted thereto if the cable is pulled or twisted; and in order to accomplish these advantageous results I have provided in each of the sections of the connector plug adjacent the rear opening thereof through which the extension cord extends into the connector block, anchoring means adapted to bind or bite into exterior portions of the ca'ble or extension cord that is clamped between the sections for iirmly gripping and holding the -cord preferably at oppositely disposed points upon sections of the plug in opposed face to face relation whereby any force applied to the cable will be vborne by such anchoring and gripping means of the plug and will so relieve the cord within the plug that these forces will not be imposed to a substantial -degree or a degree to cause detrimental movement upon the connector wires within the plug, all of which may be done in a molding operation of the-sections; and the following is a more detailed Idescription of the-present embodiment of this invention, illustrating the preferred means by which these advantageous results may be accomplished.

With reference to the drawing, I0 designates generally the electrical cord connector or attachment plug and comprises a body member generally oblong in cross-section formed of opposed halves or sections and I2 of Bakelite, hard rubber or other suitable hard insulating material. The sections and I2 are of substantially identical construction and they are* held in face to face contact with each other by means of suitable screws I4 and nuts, as is the usual construction of such connector plugs. The opposed abutting faces of the sections II and I2 are formed with spaced complementary longitudinal grooves or recesses of generally rectangular crosssection and I8 which cooperate to form parallel contact housing channels'or sockets extending inwardly from the forward end of the connector plug when the body pieces II and I2 are clamped together. The shape of these channels is not material so long as they receive and generally t the contacts of the plug.

In each of these sockets in the front of the insulating plug comprising sections and I2 there is mounted a pair of opposed resilient metal contacts 2B and 2| which are of the usual construction employed for connector plugs of this type, and arel of substantially semi-tubular formation from sheet stock. The contacts 2|! and 2| each present split terminal sockets for the reception ofthe contact prongs or blades carried by the electrical appliance. As shown in Fig. 2, the inner ends of each pair of the contacts 20 and 2| are attened, as indicated at 22, and they are xed to the plug consisting of sections and I2 in any suitable and well-known manner. The grooves I'| and I8 in the sections II and I2 are of a size sufcient to leave a slight clearance between the contact strips 20 and 2| respectively, in order to permit the same to expand laterally when in tight gripping engagement with the inserted terminal pins, blades or prongs of the usual appliance. Y

As shown in Fig. 3, each section of the plu body is hollow and provided with a laterally disposed chamber of suitable wire receiving formation for accommodating the connector wires of the extension cord C, the forward portion of the chamber 25 communicating with the rear end portions of the recesses I1 and IS to permit passage of the connector wires for attachment to the wiring terminal ends of said contacts 2i] and 2|. Formed in the rear wall of the sections are a series of axially disposed semi-cylindrical recesses 26 andv2'| which are of stepped formation and which provideV in the assembly of the sections of the plug cylindrical openings. These openings communicate with the chamber 25 in the plug by means of an axially disposed recess 28 provided in the section I2. The opening 21 is made of larger diameter than the opening 26 and is adapted to receive and hold the usual iianged sleeve, not shown, through which the extension cord C extends into the interior of the connector plug, and in which the usual cord encircling spring, not shown, is anchored, as the common construction of such cord connector plugs.

In order to tightly grip and anchor the cord secured to the plug connector against considerable torsional movement or excessive outward pulling and to prevent the transmission of strain to the connector wires and contacts within the plug, the inner surface of section is provided with a projection 38 to fit into the recess 28 and yet leave a space between the recess and projection when assembled for the accommodation of a cord which will be deformed when the cord is assembled between the two sections into such a formation that twisting or pulling strain will not be transmitted into the connection with the contacts 2l] and 2| at the points 22.

The recess 28 is provided with further recesses 4|), 4| and 42 and the projection 38 is provided with additional smaller projections or spurs 43, 44 and 45 opposite these recesses 40, 4| and 42 to further deform the cord or pierce the outer surface thereof toadditionally hold it rmly in position. y

The foregoing description is directed solely towards the construction illustrated, but I desire it to be understood that I reserve the privilege of resorting to all the mechanica1 changes to which the device is susceptible, the invention being defined and limited only by the terms of the appended claim.

Il claim:

An electrical cord connector plug comprising a body of insulating material formed in two members each having an abutting face to contact the other, said members providing complementary recesses at one end forming contact housing channels when the body pieces are together, said body members being provided at the other end with a passage at the rear end of the plug body communicating with said channels providing an entrance for the connector wires of an extension cord for connection to the wiring terminals of the contact members, said passage being formed by a main recess and a plurality of minor recesses in one member and a plurality of projections on the other member extending into said recess and but partially into the minor recesses to leave an opening of a character to deform acorclV positionedin said opening and cause grippingfof the same sufliciently to prevent substantial twisting of the cord in the opening or slipping of the cord relative to the body members.

GUY H. BURT. 

